Cholera

Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It is a disease of poverty, closely linked to poor sanitation and lack of clean drinking water. It has a short incubation period of a few hours to five days, and is characterized in the majority of cases by acute, profuse watery diarrhoea lasting from one to a few days. In its extreme form, cholera can be rapidly fatal. The disease occurs in both endemic and epidemics patterns. Cholera incidence worldwide has increased steadily since 2005 with outbreaks affecting several continents. Further, its impact can be dramatic in areas where basic environmental infrastructures are disrupted or have been destroyed and provision of potable water and sanitation is challenging. As such acute humanitarian emergencies are a particular risk factor for cholera outbreaks. The annual burden of cholera has been estimated at 1.4 to 4.3 million cases and 28 000 to 142 000 deaths worldwide (2012).

Two types of oral cholera vaccines (OCVs) are currently recommended for use by WHO. The first, a monovalent vaccine based on formalin and heat-killed whole cells of V. cholerae O1 plus recombinant cholera toxin B subunit, provides short-term protection in all age groups evaluated at 4-6 months following vaccination. It also provides short-term protection against enterotoxigenic E coli (ETEC). The second type is a bivalent vaccine based on V. cholerae serogroups O1 and O139 for which evidence of efficacy persisting over 5 years follow-up in children under five years of age at vaccination has been reported (2013).

WHO recommends cholera vaccination should be used in conjunction with other prevention and control strategies in endemic settings and in areas at risk for outbreaks. A global OCV stockpile has been created to increase access to OCVs in outbreak situations and in endemic settings.

Several cholera vaccines are being developed, mainly live attenuated vaccines that have the potential of providing longer term protection with an easy-to-administer single dose schedule.